/* 页眉定义 */
.header {
    background-color: #f1f1f1;
    padding: 5px;
    text-align: center;
}


.big_box {
    display: flex;
}

/* 侧边导航栏 */
.side_nav{
    width: 30%;
    min-width: 300px; /* 设置最小宽度防止文字被压缩 */
    background-color: #f1f1f1;
    overflow: auto;
}

/* 导航栏一级标题 */
.nav_lvl1 {
    line-height: 60px;
    cursor: pointer;
    font-size: 22px;
    text-align: left;
}

.nav_lvl1:hover{
    background-color: #bababa;
}

.nav_lvl1_text{
    white-space: nowrap;/*设置文本不换行*/
    margin-left: 5%;
}

.nav_lvl1_img{
    display: inline-block;
    margin: auto 0px;
}

/* 导航栏二级标题box */
.nav_lvl2_box{
    cursor: pointer;
    display: none;
}

.item2{
    margin:20px auto;
}
.item2:hover{
    background-color: #15305a;
}
.item2_text{
    font-size: 20px;
    color: white;
    margin-left: 25%;
}

.content{
    width: 80%;
    height: 100vh;
    background-color: #cccccc;
}




